Heating substance susceptible to oxidation



Patented May 21, 1929.-

UNITED STATES PATENT OFFICE.

HEINRICH xornnns, or ESSEN-RUHR, GERMANY, Assr'eNon TO THE 1 m IDE- vELoPMEN'r CORPORATION, on rn'rsnunen, PENNSYLVANIA, A CORPORATION OF PENNSYLVANIA.

HEATING sUBs'rANcE sUscErrIBLE r0 OXIDATION.

No Drawing. Application filed m 6, 1921, Serial No. 482,805, and in Germany may is, 1928.

The invention relates to a process for,

heating or burning substances susceptible to oxidation, such as iron, steel, porcelain and the like; and has for its objects to prevent such oxidation and its deleterious consequences by maintaining a reducing atmosphere indirect environment of such substances by the intimate contact of the substances with carbon; also to do this without requiringa surplus amount of fuel gas and without requiring firingwith an insuflicient 7 er ob ects, forinstance rods which he on amount of air. v

In heating, for instance iron and steel,

and in burning, for instance porcelain, the,

prevention of oxidation plays an" important part, be it to avoid losses by burning or an impairment of the quality of the iron or steel, or to obviate the discoloration of the porcelain. Oxidation in this connection not only is caused by the oxygen of the 'air but also by carbonic acid and steam. In the heating of iron and steel notonly an attack on the iron itself is involved but also on the ingredients important to its quality, such as silicon, carbon and manganese. In the burning of porcelain this oxidizing "effeet shows itself in the form of a yellow coloring owing to the iron oxide which causes the final product to become spottedand discolored.

In order to avoid such oxidizing phenomena, it has been the practice heretofore to avoid a surplus of oxygen as much'as-possible durin the heatin'g;'since an exact observance o the conditions necessary for complete combustion is, of course, a practical impossibility, it was always necessary to work with a corresponding lack of air or a gas surplus, which greatly impaired the economy of the firing plant, quite aside from other practical drawbacks. In burn-ing orcelain, this so-called smoking fire makes itself felt by the heavy smoking of the chimneys, in which connection the sooty flame frequently shoots out of the chimney, thus also causing a pollution of the atmosphere i and annoyance to the neighborhood. '1

According tothe invention, in heating such substances susceptible to oxidation, a control of the. heat with the maximum efiiciency attainable in actual practice is rendered possible without an oxidation of the substances to be heated, annealed orfburnt plaeQjt-hisresult being accomplished flows off as silicate.

by maintaining inthe direct vicinity of these substances areducing atmosphere, for

,example by subjecting the respective substances, while in intimate. contact withcar bon, to the heating operation." In casethis involves, 'for instance in pre-heating ovens for ingots and the like, objects which possess large dimensions and can also undergo separate treatment in other ways, said objects are coated with a protective layer ofgraphite and clay,.while in connection withsmall- .possible to use calcined coke, since carbon is convertedpin the calcining of coke, into a not easily combustible form. A chemical action of the carbon on iron'and steel is thereby practically precluded. The layer of coke powder can be so thick that the rods are in part embedded therein. This also replaces the heretofore customary covering of the hearth of such ovens with sand which fluxes with, the resultant iron oxides and Q In connection with the heating of pipe strips to welding heat before the tube rolls, where the welding and shaping take place at the same time, a considerable loss by oxidation is incurred to-day which has an unfavorable efl'ect on the quality and production. By covering the oven hearth with calcined carbon, which has no carbonizing effeet but only protects against oxidation, and by scattering said carbon over the pipe strips, the heavy losses by oxidation are prevented aild the "production and quality of the pipes are enhanced- The pipe strips brought'to welding heat. should remain in a reducing gas atmosphere from the welding ovens to the rolls, so that no roll scale or oxide may impair the welding.

The guiding idea can be realized in a highly advantageous manner in burning porcelain or any substances which it is customary to burn in capsules. Here, while operating the fire strictly according to economic viewpoints in every other respect, the reducing atmosphere necessary is produced with- -in the capsules by adding to each capsule a certain quantity of carbon; for instance in the form of charcoal, which is made at the normal temperature, approximately 450 degrees centi-grade. This calcined carbon consumes the oxygen and takes care that a reducing atmosphere always prevails in the capsule. The amount of gas-in the capsule or glowing pot'adjusts itself inequilibrium according, to the temperature, with reference to the easily reacting carbon, in conformity with the proportions made known by Boudouard, O :C: CO(CO The receptacles, such as capsules or glowing pots, must be somewhat tightly sealed, in order that the oxidizing tuyere gases may not have free access to the material.

What is claimed is 1.' The process for heating or burning substances susceptible to oxidation, characterized by a reducing atmosphere being maintained, in direct environment of the bodies to be heated, by the intimate contact of these substances with not easily combustible carbon, to prevent oxidation, without effecting carbonizing, of-said substances and in' order to make it possible to carry out the firing with the highest, practical efiiciency, without requiring a'fuel gas surplus and lack of suf- .ficient air to support substantially complete combustion of such fuel gas.

2. The process according to claim 1, characterized by the substances to be heated, being specially surrounded with a protective layer of graphite and clay.

3. The process according to claim 1, characterized by the substances to be heated,.being embedded in comminuted hard carbon distributed on the hearth of the oven, the carbon being previously heated to such an extent that a chemical action of the carbon on the substances being subjected to heat treatment does not take placefor all practical purposes.

4. The process according to claim 1 for heating rods in the manufacture of welded iron pipes and the like, characterized by heating the rods in a reducing gas atmosphere and maintaining the rods in the reducing gas atmosphere from the ovens to the rolls so that the welding may not be weakened by roller scale or oxide.

5. The process according to claim 1 for the heat treatment of substances in capsules,

HEINRICH KOPPERS. 

